Paykoman ---
When you say "...i save it with ext .an8...," what do you mean, exactly? Whenever you save an Anim8or project file, it will automatically append the ".an8" extension, you don't need to specify it. Are you actually typing in the ".an8" extension when you save the file? If so, why not try creating a new project and just specify the base name of the file when you save it. Also, have you set up your Anim8or directories properly (File > Configuration)?
And before anybody else brings it up, have you read the manual, yet? That's always the best place to start, and keep as a reference.